THE CLIMATE DIVIDE: AUSTRALIA; Prone to Drought, But Moving Ahead On Desalination

By SETH MYDANS

Published: April 3, 2007

Looking out over a sparkling blue bay on Australia's west coast, Gary Crisp, an alchemist for the new century, saw an ocean of drinking water.

Behind him was an industrial park filled with tanks, pipes, screens, filters and chemicals for converting seawater into drinking water -- 17 percent of the water supply for this city of 1.5 million people.

As the world warms and clean water becomes a prized commodity, the Perth Seawater Desalination Plant is using the renewable resources of wind and ocean to produce it, along with a finite resource that is less available in many other countries: money.

The $313 million plant, among the largest in world (behind giant plants in Israel and the United Arab Emirates), opened in November and is already running at capacity, producing up to 38 million gallons of water a day, nearly enough to fill 100 Olympic-size swimming pools.

The seawater is sucked into the plant through a pipeline whose mouth is 200 yards offshore. Once inside, it is filtered through fine membranes in a complex process called reverse osmosis.

About half the water is purified and sent into the city water system to mingle with water from other sources. The salt remains in the other half, which is flushed back out to the ocean.

The plant is one of the newest in a rapid spread of desalination plants in countries that can afford them. Though the plants are expensive to build, water from them costs only $3.50 per 1,000 gallons. They are commonplace in the Middle East, where oil pays for water, and Southern California is home to many smaller plants. What sets the Perth plant apart is not only its size but its engine -- wind power.

The plant is driven by power from 48 turbines in the Emu Downs Wind Farm, about 100 miles to the north, that can produce 80 megawatts of electricity a day, more than three times the needs of the plant. That avoids the trade-off at most desalination plants, which are powered by fossil fuels that produce greenhouse gases.

The treated water offers people here in the world's most arid continent ''security through diversity,'' in the local phrase, complementing dams, aquifers and recycling. Water conservation could be a powerful tool, but few politicians dare to suggest any measures more aggressive than limiting the use of lawn sprinklers -- a privation Perth's plant is helping to avoid.

Half the water used domestically in Perth goes to gardens, Mr. Crisp said; of the water used indoors, 30 percent goes into washing machines. Affluent suburbs use twice as much water as the city proper, he said.

Australia is suffering some of the worst droughts in its recorded history. Stream flows into dams in Perth have shrunk by two-thirds in the last 30 years, even as its population swells by more than 20,000 people a year.

Perth is talking about building one or two more plants in the coming years, and similar plants are in the early stages of development in Sydney and the town of Tugun in Queensland.

Having proved itself, the plant will have its official opening next month. Standing by the sparkling blue bay, people will be invited to drink from small plastic bottles bearing labels that read, ''Limited edition desalinated water from the Perth Seawater Desalination Plant.'' SETH MYDANS